1. Field of the Invention
This invention relates to a microcomputer-based control device incorporated in an equipment for controlling the operation of the equipment, and more particularly to such a microcomputer-based control device having a non-volatile memory into which data stored in the device is transferred to be stored.
2. Description of the prior art
In the microcomputer-based control device of the above-described type, an internally stored data such as data of a cumulative operation time period is written into a non-volatile memory at predetermined intervals in order that the data is preserved even in the occurrence of a service interruption or any other kind of interruption to a power source. Alternatively, the data is written into the non-volatile memory every time the control device is deenergized, whereby the data protection is provided.
On the other hand, an air conditioning equipment such as air cleaners which is one of the equipment controlled by a microcomputer employs methods of detecting a time of replacement of a replaceable air filter used in it. For example, in one of such methods, the color of the air filter in use is visually compared with a reference color by a user and the time of replacement of the air filter is determined to come when the user judges that the color of the air filter has changed to be tinged with the reference color. However, in this method, the user needs to visually check the color of the air filter frequently, which is troublesome. Furthermore, it is difficult for the user to make a proper judgment since the judgment relies upon delicate difference between the colors.
In order to overcome the above-described disadvantage of the air conditioning equipment, an arrangement has been proposed wherein an air-conditioning operation time period of the air conditioner is cumulatively counted and the time of replacement of the air filter is determined when the cumulative operation time period has reached a predetermined time period. In this case, too, data of the cumulative air-conditioning operation time period is written into the non-volatile memory at predetermined intervals in order that the data is preserved even in the occurrence of a service interruption or any other kind of interruption to a power source, or the data is written into the non-volatile memory every time the control device is deenergized.
The disappearance of the data due to the service interruption or any other sudden interruption of the power source is not frequent Nevertheless, the data is frequently written into the non-volatile memory when the above-described conventional method is employed for preservation of the data in the microcomputer-based control device. Consequently, the service life of the non-volatile memory is excessively shortened and an expensive long-lived non-volatile memory is required.
In the air conditioners, too, the life of the non-volatile memory is excessively shortened and the expensive long-lived non-volatile memory is required in the same circumference as described above.